Acetylene substituted polyamide oligomers

ABSTRACT

1. A COMPOUND HAVING THE FORMULA CHEMICAL STRUCTURE:   HC*C-R&#39;&#39;-((-CO-N(-)-CO-)&gt;R&#34;&lt;(-CO-N(-)-CO-)-R)N-(-CO-N(-)-   CO-)&gt;R&#34;&lt;(-CO-N(-R&#39;&#39;-C*CH)-CO-)   WHEREIN R IS POLY(ARYLENE ETHER) OR POLY(ARYLENE THIOETHER), R&#39;&#39; IS ARYLENE OR DIARYLENE ETHER, N IS AN AVERAGE FROM 1 TO ABOUT 10, AND R&#34; IS   -(4,5-DI(-)-1,2-PHENYLENE)- OR   -(4-(3,4-DI(-)-PHENYL-S-)-1,2-PHENYLENE)-   AND X IS C=O, CH2, O. S, OR A BOND.

United States Patent Office Patented Oct. 29, 1974 3,845,018 ACETYLENESUBSTITUTED POLYAMIDE OLIGOMERS Norman Bilow, Los Angeles, Abraham L.Landis, Northridge, and Leroy J. Miller, Canoga Park, Calif.,assigultfirs to Hughes Aircraft Company, Culver City, Cal

No Drawing. Continuation-impart of abandoned application Ser. No.347,501, Apr. 3, 1973. This application Nov. 6, 1973, Ser. No. 413,473

Int. Cl. C08g 20/32 US. Cl. 26047 CP 23 Claims ABSTRACT OF THEDISCLOSURE The present invention is directed to a novel class ofacetylene-substituted (ethynyl-substituted) polyimide oli gomers and thepolyamic acid or ester precursors thereof. The acetylene groups on theoligomers allow the compounds to be cured through addition reactionswhich result in little or no outgassing. In addition, these oligomersare self-curing with heat. The fully cured polyimides derived from theseoligomers have excellent thermal and mechanical properties at hightemperatures.

The invention herein described was made in the course of or under acontract with the United States Air Force.

RELATED APPLICATION This application is a continuation-in-part ofapplication Ser. No. 347,501 filed Apr. 3, 1973 and now abandoned. Anovel process for making compounds of Formula VII below, used asintermediates in the invention, is disclosed in application Ser. No.347,502, also filed on Apr. 3, 1973.

BACKGROUND OF THE INVENTION The patent literature has fully disclose thepreparation of polyimide oligomers and precursors by reaction ofaromatic compounds, such as pyromellitic acid and 3,3,4,4'-benzophenonetetracarboxylic acid, lower alkyl esters thereof, or thecorresponding dianhydrides, with aromatic diamines. The fully curedpolyimide compounds are relatively insoluble and intractable materials.When they are used as laminating resins, adhesives, etc., they areapplied in the 'fOrm of the polyamic acid or ester precursor and thencured. This cure step produces water or alcohol as byproduct, resultingin the formation of undesirable voids in the final composite assembly.

SUMMARY OF THE PRESENT INVENTION Our invention is directed to a class ofpolyimides and precursors thereof. The polyimide precursors may beapplied as coatings on wires or other substrates, as adhesives, or aslaminating resins. In addition, they may be used to form additioncopolymers with compounds such as terephthalonitrile N,N'-dioxide. Ineither event, the final products, e.g., coatings cured adhesives,laminates, etc., have very low void content as well as excellent thermaland physical properties.

DETAILED DESCRIPTION OF THE INVENTION The novel polyimide compounds ofthis invention have the general formula wherein n is an average valuefrom 1 to about 10, preferably from 1 to about 4, when in prepolymericor uncured form, R is poly(arylene ether), diarylene ketone, diarylenemethane, diarylene sulfone, or poly(arylene thioether) or the acetylenesubstituted derivatives thereof, R is arylene, diarylene thioether,diarylene methane, or diarylene ether, R" is and X is C=O, CH 0, S, or abond, or acetylene substituted derivatives thereof.

Our invention also includes polyimide precursors of the formula IIIwherein R, R, R" and n are defined above, and R' is H or lower alkyl,such as methyl, propyl, butyl and preferably ethyl. R" and R may alsocontain pendent ethynyl groups.

The precursors of Formula IV can be prepared in accordance with theprocesses of the prior art by reacting a stoichiometric excess of anaromatic tetracarboxylic acid, a lower alkyl tetra ester thereof, or thecorrespond ing dianhydride with a compound of the formula wherein R ispoly(arylene ether, diarylene ketone, diarylene methane, diarylenesulfone, poly(arylene thioether) or an acetylene-substituted derivativethereof. In order to increase the tractability and solubility of theacetylenesubstituted products of this invention, R will preferablycontain two or more ether or thioether linkages between arylene radicalsand/or pendent aryl substituents on an aryl ether radical. Compounds ofparticular interest are those in which R corresponds to the following:

linkage. A modification of that procedure as used in Y is equal to CECHmeta to an ether linkage. In the second ONa Br N02 Once the acetylproduct is obtained, subsequent conversion to the diamino acetylenicsubstituted compound is achieved through the corresponding steps of theprocedure in Ser. No. 347,502.

In compounds where m is 2 or more, the Y substituents may be the same ordifferent. We prefer compounds wherein the amino groups are in the metapositions because they have lower meeting points and are more tractableand soluble than the corresponding para-substituted analogs.Representative compounds having pendant aryl groups are3,3'-diamino-5-phenyl diphenyl ether, and 3,3-diamino 5-phenoxy diphenylether. Other typical diamines include 1 (3 aminophenoxy) 3(4-aminophenoxy)benzene, l,3-bis(3-aminophenoxy)benzene, and 1- 45(4-aminophenoxy)-3-(4-aminophenoxy)benzene. We have had particularlygood results with l,3-di(3-aminophenoxy)benzene in producingacetylene-substituted polyamides which have good solubility andtractability.

Utilizing a dianhydride for illustration, the reaction proceedsaccording to the following equation:

' 4 of the tetracarboxylic acid or its derivative to the aryl diamineaccording to the following chart:

Molar ratio of carboxylic acid m derivative to diamine As illustratedabove, the anhydride-capped polyamic acid or the corresponding acidorester-capped analog is reacted with a compound of the following formula:

H N-Arylene-CECH VII wherein arylene is phenylene, naphthylene, orbiphenylone. We prefer m-aminophenylacetylene,3-amino-3'ethynylbiphenyl, 4-amino-3'-ethynylbiphenyl, or 3-amino-4'-ethynyldiphenyl ether and the 3,3 and 4,4 substituted analogs thereofbecause the meta substitutions provide oligomers with lower meltingpoints, better solubility, and better melt flow properties. Theintermediate and aminoarylacetylene may be reacted in a solvent such asdimethylformamide at elevated temperatures, e.g., from about C. to aboutC. The reaction produces a reasonable yield of the polyamic acid in fromabout 1 hour to about 4 hours. The dimethylformamide solvent may then beremoved and the polyamic acid product diluted with the imidization agentsuch as acetic anhydride or a benzene-cresol mixture. When the latter isused, the reaction may be continued until Water evolution ceases, andthis can be seen by collecting the evolved water in an azeo tropic trap.In this latter mixture the reaction temperature is regulated by theboiling point of the benzene-cresol mixture. After the reaction iscompleted, the solution is cooled and the solvent removed.

The aminoarylacetylenes (VII) are partly known compounds. For instance,J. P. Critchley, [Tetrahedron, 5; 340-351 (1959], describes a study inwhich he used p aminophenylacetylene. The compounds of formula VII maybe produced by a novel process which has been developed by our co-workerRobert H. Boschan.

In one embodiment of the Boschan process, an aromatic compound havingboth nitro and acetyl substituents is reacted, preferably under reflux,with dimethylformamide and phosphorus oxychloride to convert the acetylradical to C(Cl)-=CHCHO. The reaction is exothermic and external coolingis needed to keep it at approximately room temperature. Thefi-chloro-substituted aldehyde radical is converted to -CECH byrefluxing a solution of the compound in dioxane and sodium hydroxide.The product is extracted with an organic solvent such as ether, theorganic solution is dried, the solvent is removed, and the productrecovered by vacuum distillation. The nitro group is then converted toamino by refluxing an aqueous alcohol solution of the product with atleast 6 moles of ferrous sulfate per mole of nitro compound. The productis removed by solvent extraction, e.g., ether, and purified, e.g., byvacuum distillation. The process is described in more detail inapplication Ser. No. 347,502, filed by the inventor concurrently withthe parent application for which this application is acontinuationin-part. The two applications have a common assignee.

We have obtained excellent results with the acetylenesubstitutedpolyimides of this invention. For example, they may be reacted withterephthalonitrile N,N-dioxide to form copolymers which make excellentlaminating resins and molding resins. Even more surprising, theacetylene-terminated polyimides may be used as such, even in the absenceof a catalyst or curing agent, to prepare laminates of excellentphysical properties.

The following examples are set forth to illustrate the presentinvention:

EXAMPLE I A solution of 1,3-di(3-aminophenoxy)benzene (5.80 grams,0.0198 mole) in 30 ml. of dry dimethylformamide was added dropwise to arapidly stirring solution of benzophenotetracarboxylic dianhydride(17.78 grams, 0.0397 mole) in dry dimethylformamide (50 ml.). Thesolution was heated at gentle reflux for several hours. Then,3-aminophenylacetylene (5.12 grams, 0.0438 mole) was added and themixture was heated at 80 C. for 16 hours. The solvent was removed usingthe rotary evaporator, and 100 ml. acetic anhydride was added to theresidue. The mixture was heated at reflux for several hours. Afterallowing the slurry to stand overnight, the mixture was dispersed in 350ml. of absolute ethanol, filtered and washed with fresh ethanol. Theresin was then vacuum dried to yield 14.1 grams of product.

EXAMPLE II A solution of the acetylene-substituted polyimide wasprepared by dissolving 20 grams of the resin of Example 1 in 200 ml. ofsulfolane. Then grams of terephthalonitrile N,N-dioxide was added to thesolution and the mixture was stirred at room temperature for 24 minutes.The resultant product was isolated by triturating the reaction mixturewith about 5 times its volume of absolute ethanol, filtering, andwashing the precipitated resin with fresh ethanol. The precipitatedresin was reacted for 40 minutes at 230240 C. in a vacuum. Then it wasdissolved in dimethylformamide and the lacquer was used to coat glasscloth reinforcement. A desirable resin content of the reinforcement isabout 40 percent. A multi-layer laminate was made by molding at about250 to 275 C. under vacuum bag conditions. The laminate was postcured ata temperature up to about 285 C.

EXAMPLE III A lacquer of acetylene-substituted polyimide oligomerprepared in Example I was made with dimethylformamide. The lacquer had asolids content of percent and was used to impregnate 181E glass cloth.The imprenated cloth was dried in a circulating air oven at 325 F. for afew minutes and then vacuum-dried at 275 F. for 16 hours. A seven-plylaminate was molded at 535 F., 200 p.s.i., 4 hours using a contact timeof zero minutes. The resulting laminate had a resin content of 25.9percent. It was then post-cured in air using the following cycle: 4hours at each temperature, 450 F., 500 F., 555 F. and 600 F. Anexcellent molded laminate resulted which had a final void content of 1.3percent. During the postcure the laminate lost only 0.31 percent inweight.

EXAMPLE IV A solution of 1,3-di(3-aminophenoxy)benzene (5.80 grams,0.0198 mole) in ml. of dry dimethylformamide was added dropwise to arapidly stirring solution of hemephenonetetracarboxylic dianhydride17.78 grams, 0.0397 mole) in dry dimethylformamide (50 ml.). Thesolution was heated at gentle reflux for several hours. Then, 3-aminophenoxyphenylacetylene (9.16 grams, 0.0438 mole) was added and themixture was heated at 80 C. for 16 hours. The solvent was removed usingthe rotary evaporator, and 100 ml. acetic anhydride was added to theresidue. The mixture was heated at reflux for several hours. Afterallowing the slurry to stand overnight, the mixture was dispersed in 350ml. of absolute ethanol, filtered and washed with fresh ethanol. Theresin was then vacuum dried to yield 18 grams of product.

EXAMPLE V A lacquer of acetylene-terminated polyimide oligomer similarto that prepared in Example IV in dimethylformamide, having a solidscontent of 15.percent, was used to impregnate 181E glass cloth having anA-1100 finish. The impregnated cloth was dried in a circulating air ovenat 325 F. for a few minutes and then vacuum-dried at 275 F. for 16hours. A seven-ply laminate was molded at 535 F., 200 p.s.i., 4 hours.The resulting laminate had a resin content of 26 percent. It was thenpost-cured in air using the following cycle: 4 hours at eachtemperature, 450 F., 500 F., 550 F., and 600 F An excellent moldedlaminate resulted which had a final void content of about 1 percent.During the post-cure the laminate lost less than one percent in weight.

EXAMPLE VI Preparation of 1,3-di'(3-nitr0phenoxy)benzene Sodiummethoxide was prepared by adding absolute methanol (70 g., 2.2 moles) indry benzene (250- ml.) to a rapidly stirred dispersion of sodium sand(46.0 g., 2.0 moles) in dry benzene (1000 ml.). The reaction mixturerefluxed gently during the addition. Based on the absence of any graycolor from unreacted sodium, the reaction was complete in about 2 hours.Then the freshly prepared sodium methoxide slurry in benzene was addedto a dispersion of dry resorcinol g., 1.00 mole) in dry benzene (1000ml.) and the solution heated to reflux for several hours while stirringvigorously. The solvent was removed under argon, using an oil bath at110 C. The final traces of solvent were removed by vacuum distillation.After the sodium resorcinate had cooled to room temperature, finelypowdered cuprous chloride (34.6 g.) and a deaerated solution of1-bromo-3-nitrobenzene (450 g., 2.20 moles) in pyridine (2000 ml.) wereadded and the mixture was heated by reflux under argon for 8 hours,cooled and filtered to remove inorganic salts. The filtrate wasconcentrated to about onequarter of its volume on the rotary evaporator,diluted with benzene (1 liter) and washed in a separatory funnelsuccessively with 1:1 hydrochloric acid, water, 10 percent aqueoussodium hydroxide, and water. The solvent was removed on the rotaryevaporator. The resulting oily residue was then triturated with severalportions of cold ethanol (0 C.), which eifectively dissolved theunreacted 1-bromo-3-nitrobenzene. The product, 1,3-di-(3-nitrophenoxy)benzene, was recrystallized from ethanol. A yield of 146g. (41.4 percent yield), mp. 101- 103 C., was obtained.

Preparation of 2,4-di(3-nitrophenoxy)acetophenone This method involvedthe acetylation of 1,3-di(3-nitrophenoxy)benzene with acetyl chloridecatalyzed by aluminum chloride. To a solution of 1,3-di(3-nitrophenoxy)benzene (176 g., 0.50 mole) in 1,2-dichloroethane (250 ml.) was addedanhydrous aluminum chloride 147 g., 1.10 moles). Then acetyl chloride(43 g., 0.55 mole) was added dropwise over a 1.5-hour period while thetemperature of the reaction mixture was kept at 05 C. by externalcooling. After the addition of the acetyl chloride was completed, anadditional 3 g. of acetyl chloride was added to compensate for any lossfrom the hydrogen chloride evolution. The reaction mixture was allowedto come to room temperature and remain at room temperature for 1 hour.After this time the temperature was raised to 65 C. and held there for45 minutes. The reaction mixture was added to about 1000 g. of crushedice and the oily layer extracted with benzene. The benzene extract wasevaporated on the rotary evaporator and the residue recrystallized fromethanol to yield .121 g. of product, m.p. -121 C. This represents a 63.4percent yield.

Preparation of 1-(2-forrnyl-l-chlorovinyl)-2,4- bis 3 -nitrophenoxy)benzene Phosphorus oxychloride (34.8 g., 0.23 mole) was added todimethyl-formamide (60 ml.) with constant stirring. The reaction mixtureWas maintained at room temperature. It was stirred for an additional 1.5hours.

Then a solution of 2,4-di(3-nitrophenoxy)acetophenone (60.0 g., 0.15mole) in warm dimethylformamide (100 ml.) was added dropwise. Thereaction temperature was maintained at 40-42. C. during the addition toprevent precipitation. The solution was kept at room temperature forseveral days. It was then added to an ice-cold saturated aqueoussolution of sodium bicarbonate and the solution extracted with benzene.The benzene extract was then washed with water, dried with anhydrouspotassium carbonate and evaporated on the rotary evaporator. A portionof the residue was recrystallized from isopropyl alcohol. The yellowcrystals had a wide melting range starting at about 100 C. This isprobably due to the presence of several isomers.

Preparation of 2-4-di(3-nitrophenoxy)phenylacetylene To a refluxingsolution of sodium hydroxide (4.0 g., 0.10 mole) in water (50' ml.) wasadded a solution of 1-(2-formyl-1-chlorovinyl) 2,4 bis (3-nitrophenoxy)benzene made above in dioxane (50 ml.) at such a rate that refluxing didnot stop. The addition required 45 minutes. The solution was heated atreflux for an additional 30 minutes. After cooling the solution it wasextracted with ether. The ether extract was evaporated on the rotaryevaporator to yield 12.4 grams of product. This product was thenrecrystallized from ethanol to yield an amber product that had a verywide melting point range. It started to melt at 72 C. and was completelymolten at 107 C.

Preparation of 2,4-di(3-aminophenoxy)phenylacetylene To a refluxingsolution of ferrous sulfate heptahydrate (59.2 g., 0.213 mole) in water(125 ml.) was added, over a period of 45 minutes, a solution of2,4-di(3- nitrophenoxy)phenylacetylene (10.0 g., 0.027 mole) in 175 ml.of dioxane. Refluxing was continued for an additional 2 /2 hours afterwhich concentrated ammonium hydroxide (40 ml.) was added. Refluxing wascontinued under argon for 16 hours, and the mixture was cooled andextracted with ether. The ether extract was dried with Drierite andevaporated to dryness. The light brown solid was weighed and the yieldindicated that the reduction had taken place almost quintitatively.After purification by chromatography the compound was used to preparepolyirnide oligomers.

What is claimed is:

1. A compound having the following chemical structure:

wherein R is poly(arylene ether) or poly(arylene thioether), R isarylene or diarylene ether, 11 is an average from 1 to about 10, and R"is III and X is :0, CH 0. S, or a bond.

2. The compound of claim 1 wherein n is an average of 1 to about 4.

3. A compound of claim 1 wherein R is phenylene.

4. A compound of claim 3 wherein each acetylene group is in metaposition with respect to an amide group.

5. A compound of claim 4 wherein R is Y m V wherein X is O or S, Y is Hor CECH, each imide group is attached in meta or para position withrespect to an ether or thioether linkage and m is 0 to about 4.

6. A compound of claim 5 wherein at least one Y is CEH.

7. A compound of claim 5 wherein R" is 8. A compound of claim 2 whereinR is i o 2 and each imide group is attached in meta or para positionwith respect to an ether linkage.

9. A compound of claim 8 wherein each acetylene group is in metaposition with respect to the ether linkage.

10. A compound of claim 9 wherein R is L n n wherein R is diaryleneether or diarylene thioether, R is arylene or diarylene ether, 11 is anaverage from 1 to about 4, R" is III X is C=O, CH 0, S, or a bond and R'is H or a lower alkyl.

16. A compound of claim 15 wherein n is an average of about 1. Y

17. A compound of claim 15 wherein R is phenylene.

18. A compound of claim 16 wherein each acetylenic group is in metaposition with respect to the nitrogen atom.

19. A compound of claim 17 wherein R is wherein X is 0 or S, Y is H orCEH, m is 0 to about 4, and each nitrogen atom is attached in meta orpara position with respect to an ether linkaze.

20. A compound of claim 15 wherein R is a mixture of R groups.

21. A compound of claim 16 wherein -R' is a mixture of R groups.

22. A compound of claim 15 wherein R is a mixture R" groups. 23. Acompound of claim 15 wherein R is a mixture of R groups.

References Cited UNITED STATES PATENTS 3,516,967 6/1970 Funer 260473,526,610 9/1970 Bower 260-75 LESTER L. LEE, Primary Examiner US. Cl.X.R.

16l197, 227; 26032.6 N, 47 CZ, 49, 63 N, 65, 78 TF, 78 UA. 326 N Column8, line 2, Column 8,

zgjggi UNITED STATES PATENT OFFICE @ETIFKCATE 9F CORRECHN Patent No 3,845, 018 Dated October 29, 1974 Inventor) NORMAN BILOW ET AL It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

I h the Title,

Column 1, line 37,

should read -POLYIMIDE.

should read -disclosed--.

"POLYAMIDE" "disclose" Column 2, the structures shown in lines 20-34should be connected so that Q R}NH- C Column 2, line 47, "(aryleneether," should read --(arylene ether) Column 2, line 71, "as used in Yis" should read --is used when Y is.

Column 3, the structure shown in lines 52-73 should be identified by"VI" Column 5, line 44, "imprenated" should read -impregnated--.

Column 5, line 51, "555 F" should read --55O F.

Column 6, line 50, a hyphen should be inserted after"l,3-di(3nitrophenoxy)".

Column 7, line 19, a hyphen should be inserted after (3-nitrophenoxy)".

Column 7, line 43, "quintitatively" should read -quantitatively--.Column 7 line 72, "and X is C=O, CH 0. S, or a bond."

should read --and X is C=O, CH 0, S, or a bond--.

"amide" should read --imide-. in the structure shown in lines 49-61, thefollowing: CR' should read HC CR' III l C-NN R should read C NH-R O Oand the structures should be connected so that RLNH-8 Column 9, in thestructural formula shown in lines 10-15,

the floating bond should have a "Y" attached,

LColumn 10, line 3, "Claim 16" should read --Claim l5. .J

fiigned and Sealed thisthirtieth D a); of March 1 9 76 [SE AL] Attest:

' RUTH c. MASON A nesting Officer C. MARSHALL DANN (mnmissimzcrufParents and Trademarks

1. A COMPOUND HAVING THE FORMULA CHEMICAL STRUCTURE: 